Various injectors incorporated with the ignition device and the fuel injection device are currently suggested. These are expected to use for the direct injection engine with regard to the diesel engine, the gas engine, or the gasoline engine. The injector incorporated with the ignition device is largely divided into coaxial structural type that the axial center of the injector (fuel injection device) is coincide with the axial center of the center electrode of the spark plug used for the ignition device, and alignment in parallel structural type that the fuel injection device and the ignition device are arranged in parallel and housed inside one casing. The coaxial structural type is disclosed in, for example, in Patent Documents 1 and 2. In the coaxial structural type, the center electrode of the spark plug used as the ignition device is constituted into a hollow type with step which the sheet member is formed at the tip end, and it is constituted such that the needle for opening/closing the sheet member by operation of the actuator is inserted into the center electrode. There is the advantage for easier mounting to the internal combustion chamber.
Moreover, the alignment in parallel structural type is disclosed in, for example, Patent Documents 3 and 4. In the alignment in parallel structural type, the fuel injection device and the spark plug used for the ignition device are aligned inside the cylindrical casing with the predetermined interval, and it is constituted such that the generally-used fuel injection device and the spark plug can be used together. Therefore, there is the advantage that each of the fuel injection device and the ignition plug is not required for being designed newly.